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30 * @Id: tabs.1,v 1.52 2023/12/23 16:08:25 tom Exp @
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37 <TITLE>tabs 1 2023-12-23 ncurses 6.4 User commands</TITLE>
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42 <H1 class="no-header">tabs 1 2023-12-23 ncurses 6.4 User commands</H1>
44 <STRONG><A HREF="tabs.1.html">tabs(1)</A></STRONG> User commands <STRONG><A HREF="tabs.1.html">tabs(1)</A></STRONG>
49 </PRE><H2><a name="h2-NAME">NAME</a></H2><PRE>
50 <STRONG>tabs</STRONG> - set terminal tab stops
53 </PRE><H2><a name="h2-SYNOPSIS">SYNOPSIS</a></H2><PRE>
54 <STRONG>tabs</STRONG> [<EM>options</EM>] [<EM>tabstop-list</EM>]
57 </PRE><H2><a name="h2-DESCRIPTION">DESCRIPTION</a></H2><PRE>
58 The <STRONG>tabs</STRONG> program clears and sets tab-stops on the terminal. This uses
59 the terminfo <STRONG>clear_all_tabs</STRONG> and <STRONG>set_tab</STRONG> capabilities. If either is
60 absent, <STRONG>tabs</STRONG> is unable to clear/set tab-stops. The terminal should be
61 configured to use hard tabs, e.g.,
65 Like <STRONG><A HREF="clear.1.html">clear(1)</A></STRONG>, <STRONG>tabs</STRONG> writes to the standard output. You can redirect
66 the standard output to a file (which prevents <STRONG>tabs</STRONG> from actually
67 changing the tabstops), and later <STRONG>cat</STRONG> the file to the screen, setting
68 tabstops at that point.
70 These are hardware tabs, which cannot be queried rapidly by
71 applications running in the terminal, if at all. Curses and other
72 full-screen applications may use hardware tabs in optimizing their
73 output to the terminal. If the hardware tabstops differ from the
74 information in the terminal database, the result is unpredictable.
75 Before running curses programs, you should either reset tab-stops to
80 or use the <STRONG>reset</STRONG> program, since the normal initialization sequences do
81 not ensure that tab-stops are reset.
84 </PRE><H2><a name="h2-OPTIONS">OPTIONS</a></H2><PRE>
86 </PRE><H3><a name="h3-General-Options">General Options</a></H3><PRE>
87 <STRONG>-T</STRONG><EM>name</EM>
88 Tell <STRONG>tabs</STRONG> which terminal type to use. If this option is not
89 given, <STRONG>tabs</STRONG> will use the <STRONG>$TERM</STRONG> environment variable. If that is
90 not set, it will use the <EM>ansi+tabs</EM> entry.
92 <STRONG>-d</STRONG> The debugging option shows a ruler line, followed by two data
93 lines. The first data line shows the expected tab-stops marked
94 with asterisks. The second data line shows the actual tab-stops,
95 marked with asterisks.
97 <STRONG>-n</STRONG> This option tells <STRONG>tabs</STRONG> to check the options and run any debugging
98 option, but not to modify the terminal settings.
100 <STRONG>-V</STRONG> reports the version of <EM>ncurses</EM> which was used in this program, and
103 The <STRONG>tabs</STRONG> program processes a single list of tab stops. The last option
104 to be processed which defines a list is the one that determines the
105 list to be processed.
108 </PRE><H3><a name="h3-Implicit-Lists">Implicit Lists</a></H3><PRE>
109 Use a single number as an option, e.g., "<STRONG>-5</STRONG>" to set tabs at the given
110 interval (in this case 1, 6, 11, 16, 21, etc.). Tabs are repeated up
111 to the right margin of the screen.
113 Use "<STRONG>-0</STRONG>" to clear all tabs.
115 Use "<STRONG>-8</STRONG>" to set tabs to the standard interval.
118 </PRE><H3><a name="h3-Explicit-Lists">Explicit Lists</a></H3><PRE>
119 An explicit list can be defined after the options (this does not use a
120 "-"). The values in the list must be in increasing numeric order, and
121 greater than zero. They are separated by a comma or a blank, for
127 Use a "+" to treat a number as an increment relative to the previous
132 which is equivalent to the 1,6,11,16,21 example.
135 </PRE><H3><a name="h3-Predefined-Tab-Stops">Predefined Tab Stops</a></H3><PRE>
136 POSIX defines several predefined lists of tab stops.
138 <STRONG>-a</STRONG> Assembler, IBM S/370, first format
141 <STRONG>-a2</STRONG> Assembler, IBM S/370, second format
144 <STRONG>-c</STRONG> COBOL, normal format
147 <STRONG>-c2</STRONG> COBOL compact format
150 <STRONG>-c3</STRONG> COBOL compact format extended
151 1,6,10,14,18,22,26,30,34,38,42,46,50,54,58,62,67
153 <STRONG>-f</STRONG> FORTRAN
156 <STRONG>-p</STRONG> PL/I
157 1,5,9,13,17,21,25,29,33,37,41,45,49,53,57,61
159 <STRONG>-s</STRONG> SNOBOL
162 <STRONG>-u</STRONG> UNIVAC 1100 Assembler
166 </PRE><H3><a name="h3-Margins">Margins</a></H3><PRE>
167 A few terminals provide the capability for changing their left/right
168 margins. The tabs program has an option to use this feature:
170 <STRONG>+m</STRONG> <EM>margin</EM>
171 The effect depends on whether the terminal has the margin
174 <STRONG>o</STRONG> If the terminal provides the capability for setting the left
175 margin, tabs uses this, and adjusts the available width for
178 <STRONG>o</STRONG> If the terminal does not provide the margin capabilities, tabs
179 imitates the effect, putting the tab stops at the appropriate
180 place on each line. The terminal's left-margin is not
183 If the <EM>margin</EM> parameter is omitted, the default is 10. Use <STRONG>+m0</STRONG> to
184 reset the left margin, i.e., to the left edge of the terminal's
185 display. Before setting a left-margin, tabs resets the margin to
186 reduce problems which might arise on moving the cursor before the
189 When setting or resetting the left-margin, tabs may reset the right-
193 </PRE><H2><a name="h2-FILES">FILES</a></H2><PRE>
194 <EM>/usr/share/tabset</EM>
195 tab stop initialization database
198 </PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
199 <EM>IEEE</EM> <EM>Std</EM> <EM>1003.1/The</EM> <EM>Open</EM> <EM>Group</EM> <EM>Base</EM> <EM>Specifications</EM> <EM>Issue</EM> <EM>7</EM>
200 (POSIX.1-2008) describes a <STRONG>tabs</STRONG> utility. However
202 <STRONG>o</STRONG> This standard describes a <STRONG>+m</STRONG> option, to set a terminal's left-
203 margin. Very few of the entries in the terminal database provide
204 the <STRONG>smgl</STRONG> (<STRONG>set_left_margin</STRONG>) or <STRONG>smglp</STRONG> (<STRONG>set_left_margin_parm</STRONG>)
205 capability needed to support the feature.
207 <STRONG>o</STRONG> There is no counterpart in X/Open Curses Issue 7 for this utility,
208 unlike <STRONG><A HREF="tput.1.html">tput(1)</A></STRONG>.
210 The <STRONG>-d</STRONG> (debug) and <STRONG>-n</STRONG> (no-op) options are extensions not provided by
211 other implementations.
214 </PRE><H2><a name="h2-HISTORY">HISTORY</a></H2><PRE>
215 A <STRONG>tabs</STRONG> utility appeared in PWB/Unix 1.0 (1977). A reduced version
216 shipped in Seventh Edition Unix (early 1979) and in 3BSD (later the
217 same year); it supported a "-n" option to set the first tab stop at the
218 left margin. That option is not documented by POSIX.
220 The PWB/Unix <STRONG>tabs</STRONG> utility returned in System III (1980), and used
221 built-in tables rather than the terminal database, to support a half-
222 dozen hardcopy terminal (printer) types. It also had built-in logic to
223 support setting the left margin, as well as a feature for copying the
224 tab settings from a file.
226 Versions of the program in later releases of AT&T Unix, such as SVr4,
227 added support for the terminal database, but retained the tables to
228 support the printers. In an earlier development effort, the tab stop
229 initialization provided by <STRONG><A HREF="tset.1.html">tset(1)</A></STRONG> (1982), and incorporated into
230 <STRONG><A HREF="tput.1.html">tput(1)</A></STRONG> uses the terminal database,
232 The <STRONG>+m</STRONG> option was documented in the POSIX Base Specifications Issue 5
233 (Unix98, 1997), then omitted in Issue 6 (Unix03, 2004) without express
234 motivation, though an introductory comment <EM>"and</EM> <EM>optionally</EM> <EM>adjusts</EM> <EM>the</EM>
235 <EM>margin"</EM> remains, overlooked in the removal. The <STRONG>tabs</STRONG> utility
236 documented in Issues 6 and later has no mechanism for setting margins.
237 The <STRONG>+m</STRONG> option in <EM>ncurses</EM> <STRONG>tabs</STRONG> differs from the SVr4 feature by using
238 terminal capabilities rather than built-in tables.
240 POSIX documents no limit on the number of tab stops. Other
241 implementations impose one; the limit is 20 in PWB/Unix's <STRONG>tabs</STRONG> utility.
242 While some terminals may not accept an arbitrary number of tab stops,
243 <EM>ncurses</EM> <STRONG>tabs</STRONG> attempts to set tab stops up to the right margin if the
244 list thereof is sufficiently long.
246 The "Rationale" section of the Issue 6 <STRONG>tabs</STRONG> reference page details how
247 the committee considered redesigning the <STRONG>tabs</STRONG> and <STRONG>tput</STRONG> utilities,
248 without settling on an improved solution. It claims that
250 no known historical version of tabs supports the capability of
251 setting arbitrary tab stops.
253 Nevertheless, the feature described in subsection "Explicit Lists"
254 above was implemented in PWB/Unix, and permits the setting of abitrary
258 </PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE>
259 <STRONG><A HREF="infocmp.1m.html">infocmp(1m)</A></STRONG>, <STRONG><A HREF="tset.1.html">tset(1)</A></STRONG>, <STRONG><A HREF="ncurses.3x.html">curses(3x)</A></STRONG>, <STRONG><A HREF="terminfo.5.html">terminfo(5)</A></STRONG>
263 ncurses 6.4 2023-12-23 <STRONG><A HREF="tabs.1.html">tabs(1)</A></STRONG>
267 <li><a href="#h2-NAME">NAME</a></li>
268 <li><a href="#h2-SYNOPSIS">SYNOPSIS</a></li>
269 <li><a href="#h2-DESCRIPTION">DESCRIPTION</a></li>
270 <li><a href="#h2-OPTIONS">OPTIONS</a>
272 <li><a href="#h3-General-Options">General Options</a></li>
273 <li><a href="#h3-Implicit-Lists">Implicit Lists</a></li>
274 <li><a href="#h3-Explicit-Lists">Explicit Lists</a></li>
275 <li><a href="#h3-Predefined-Tab-Stops">Predefined Tab Stops</a></li>
276 <li><a href="#h3-Margins">Margins</a></li>
279 <li><a href="#h2-FILES">FILES</a></li>
280 <li><a href="#h2-PORTABILITY">PORTABILITY</a></li>
281 <li><a href="#h2-HISTORY">HISTORY</a></li>
282 <li><a href="#h2-SEE-ALSO">SEE ALSO</a></li>